Effect of exercise on uterine blood flow in the pregnant Pygmy goat

Pygmy goats in the last third of pregnancy were trained to walk on a treadmill at rates up to 2.0 mph and up an inclination of 0-15 degrees. Electromagnetic flowmeters were placed unilaterally on a uterine artery, and measurements were made while the goats were standing quietly on the treadmill and during 5 min of exercise. Blood flow fell during exercise in all five animals studied, and this reduction was proportional to the level of exertion. At the highest level of exercise that these animals would voluntarily perform, uterine artery blood flow fell by 32 +/- 3 (SE) % (P less than 0.001) from control. In four additional animals the radioactive microsphere technique was used to measure uterine blood flow at rest and after 5-7 min of exercise. In these animals, exercise caused total uterine blood flow to fall by 18 +/- 10%; cotyledonary (placental) blood flow fell by 8 +/- 13%, while myoendometrial blood flow decreased by 52 +/- 12% (P less than 0.05). Thus nonplacental portions of the pregnant Pygmy goat uterus suffer major reductions in blood flow during exercise. This vasoconstriction may be due to exercise per se or to concomitant hypocapnia or hyperthermia. Singleton and twin kids born to animals that exercised were of normal birth weight.